1. Field of the Invention
The invention relates to drafting machines which are useful, in general, as a means of aiding in engineering drawing work, so as to quickly and accurately measure and draw straight lines between desired points, and more particularly, to improvements in track type drafting machines.
2. Description of the Prior Art
A draftsman/designer's productive time may generally be divided into two broad catagories; namely, creative or thinking time, and physical or drawing time. The present invention is concerned with reducing the physical or drawing time.
In using a typical track type drafting machine, once the drafting machine head is moved away from its particular point, there is no way of determining the relationship of a new point at a new location to the old point unless the draftsman marks the new point and measures the distance back to the old point with the individual scales and some construction lines. In the same manner, the only reasonably accurate method of laying out a second point in relation to a first point is by drawing a base line, measuring one dimension along it and marking a point thereon, then drawing a perpendicular line at this point and measuring the other dimension along the perpendicular line. For example, if a draftsman desired to lay out point B, 6 inches horizontally and 3 inches vertically from point A, the normal routine would be to draw a construction or base line through point A, measure and mark a point 6 inches from point A, draw a vertical construction line through this point and measure 3 inches up from the base line on the second or vertical construction line.
Additionally, it should be noted that when using a standard track type drafting machine, there is no dimensional relationship between the right angled scales fitted to the drafting machine head. The only way to use the horizontal scale for anything other than a straight edge is to move the zero point on the scale to some reference line or point. The same applies to the vertical scale.
It will thus be apparent that the prior art has long endeavored to develop improvements in a track type drafting machine whereby the exact location of any other point on a drawing board to which the scales are moved is immediately known in relation to a starting point. In this regard, the prior art has developed a coordinate measuring machine which utilizes optical scales and is highly accurate. However, while this machine has definite advantages, its primary disadvantages include expense of manufacture and the necessary modifications to a drafting machine and drawing board before the machine can be incorporated therewith. Additionally, the coordinate measuring machine is designed more for measuring than laying out dimensions and the cost prohibits it being marketed as a general drafting aid.
While endless tapes (see, for example, U.S. Pat. No. 3,193,195, in the name of C. S. Jeffries, Jr., and U.S. Pat. No. 2,549,634, in the name of L. V. Parsons) and common origin scales (see U.S. Pat. No. 2,551,082, in the name of H. Anderegg) are known, the prior art has never combined the teachings in such a way to develop an improved track type drafting machine wherein the exact location of any other point on a drawing board to which right-angled rules fitted to the drawing machine head are moved in relation to the starting point is immediately known.